I checked out the Sheplers website today. Now most guys here aren't into prewashed jeans, but this information is interesting:
13MWZ and 936DEN in colors stonewash and bleach are made of 15.75oz denim!! The prewash process may affect durability to some extent, but I believe these are almost as hard wearing as the rigids. Wrangler's broken twill denim is nearly indestructable, anyway.
Wrangler does a great job with their Cowboy Cut line. No wonder Levi's has lost ground in the Western segment, as Wranglers are superiour in almost every aspect.